How to make brown

At High School, the chemistry lab had sets of chemicals in squeezy bottles. Whenever there was a spare moment when we were unsupervised, we would jump out of our seats and run over to the bottles and start squirting random chemicals into test tubes or beakers in an attempt to cause some kind of chemical reaction (usually just a swift and violent reaction from the teacher, if caught, was the best we could do).

The majority of the time the chemicals stayed clear, but quite often they created a greenish-brown sludge we assigned the name "Brown". The precise nature of the Brown is unknown, and nobody had the courage (or was gullible enough) to taste or even touch it.

It remains a mystery to this day what this substance was, or even what it was made up of, but a mixture of random chemicals is bound to reproduce the substance known as "Brown".